The objective of this research project is to study the chromate-reductase activity of mitochondria, to determine the damage induced in mitochondrial DNA by chromate and to determine the effect of chromium on DNA structure. The mitochondria will serve as a model system for studying the uptake-reduction model for chromate carcinogenicity. The components of mitochondria, such as the electron transport chain or the cytochrome P-450-like activity, which are responsible for chromate metabolism will be determined using inhibitors and purified components. The generation of reactive species such as free radicals or chromium (V) during mitochondrial chromate reduction will be monitored by EPR spectroscopy. The ability of chromium to affect supercoiling and bind to specific sequences of mitochondrial (mt) DNA and pBR322 DNA will be studied by buoyant density gradient, gel electrophoresis, restriction enduclease digestion and DNA sequencing techniques. The ability of chromium to affect the B-Z DNA transition of poly (dG-dC) . poly (dG-dC) will be determined by circular dichroism. The ability of chromium to condense DNA into PsiDNA or toroidal structures will be determined by circular dichroism and sedimentation studies. Local denaturation of DNA by bound chromium will be examined by S1 nuclease sensitivity assay.